Lecture 1: Skeletal System Overview

Functions and Classification of the Skeletal System

The skeletal system provides structural support, protection, movement, mineral storage, and blood cell formation. Bones are classified by shape and function.

• Functions: Support, protection of organs, movement (leverage for muscles), mineral storage (calcium, phosphorus), hematopoiesis (blood cell formation).

• Axial Skeleton: Skull, vertebral column, rib cage.

• Appendicular Skeleton: Limbs and girdles (pectoral and pelvic).

• Bone Classification: Long, short, flat, irregular bones. Example: Femur (long), carpals (short), sternum (flat), vertebrae (irregular).

Structure of Typical Long Bones

• Diaphysis: Shaft, composed of compact bone.

• Epiphyses: Ends, mostly spongy bone.

• Metaphysis: Region between diaphysis and epiphysis; contains growth plate.

• Periosteum: Outer fibrous covering.

• Endosteum: Lining of medullary cavity.

Osseous Tissue Types and Hormonal Regulation

• Compact Bone: Dense, forms outer layer.

• Spongy Bone: Porous, found in epiphyses.

• Hormonal Regulation: Parathyroid hormone (PTH), calcitonin, sex hormones regulate bone growth and remodeling.

• Osteoporosis: Condition of reduced bone mass and increased fracture risk.

Lecture 2: Bone Remodeling and Growth

Bone Remodeling and Hormonal Control

Bone remodeling is a continuous process involving bone resorption and formation, regulated by hormones.

• Wolff's Law: Bone adapts to the loads under which it is placed.

• Hormones: PTH increases blood calcium by stimulating osteoclasts; calcitonin lowers blood calcium; sex hormones promote bone growth.

Bone Fracture Repair

• Four Stages:

  1. Hematoma formation

  2. Fibrocartilaginous callus formation

  3. Bony callus formation

  4. Bone remodeling

Bone Development and Growth

• Intramembranous Ossification: Forms flat bones (e.g., skull).

• Endochondral Ossification: Forms most bones, including long bones.

• Bone Growth: Bones grow in length at the epiphyseal plate and in thickness by appositional growth.

• Example: Femur lengthens during childhood and adolescence.

Lecture 3: Joints and Articulations

Functional Classes of Joints

Joints (articulations) are classified by the amount of movement they allow.

• Synarthroses: Immovable joints (e.g., sutures in the skull).

• Amphiarthroses: Slightly movable joints (e.g., intervertebral discs).

• Diarthroses: Freely movable joints (e.g., shoulder, knee).

Structural Classes of Joints

• Fibrous Joints: Bones joined by dense connective tissue; mostly immovable.

• Cartilaginous Joints: Bones joined by cartilage; slightly movable.

• Synovial Joints: Bones separated by a fluid-filled cavity; freely movable.

Synovial Joint Structure and Function

• Articular Capsule: Encloses joint cavity.

• Synovial Fluid: Lubricates and nourishes articular cartilage.

• Ligaments: Stabilize joints.

• Articular Cartilage: Reduces friction.

Types of Diarthroses (Synovial Joints)

• Plane, hinge, pivot, condyloid, saddle, ball-and-socket joints.

• Example: Knee (hinge), shoulder (ball-and-socket).

Lecture 4: Muscle Tissue

Types and Properties of Muscle Tissue

Muscle tissue is specialized for contraction and movement. There are three types: skeletal, cardiac, and smooth.

• Skeletal Muscle: Voluntary, striated, attached to bones.

• Cardiac Muscle: Involuntary, striated, found in heart.

• Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs.

Muscle Structure and Connective Tissue Coverings

• Epimysium: Surrounds entire muscle.

• Perimysium: Surrounds fascicles (bundles of muscle fibers).

• Endomysium: Surrounds individual muscle fibers.

• Fascicle: Bundle of muscle fibers.

Muscle Attachments

• Origin: Fixed attachment.

• Insertion: Movable attachment.

• Direct vs. Indirect Attachment: Direct (fleshy) attachment to bone; indirect via tendons or aponeuroses.

Lecture 5: Neuromuscular Junction and Muscle Contraction

Structure and Function of Neuromuscular Junction

The neuromuscular junction is the site where a motor neuron stimulates a muscle fiber to contract.

• Sequence: Action potential arrives at axon terminal, acetylcholine (ACh) released, binds to receptors on sarcolemma, initiates depolarization.

• Excitation-Contraction Coupling: Action potential triggers calcium release from sarcoplasmic reticulum, leading to muscle contraction.

• Relaxation: Calcium reuptake, cessation of ACh release.

ATP and Muscle Fiber Types

• ATP Role: Powers contraction and relaxation.

• Sources of ATP: Creatine phosphate, anaerobic glycolysis, aerobic respiration.

• Muscle Fiber Types: Slow oxidative, fast glycolytic, fast oxidative.

• Example: Marathon runners have more slow oxidative fibers; sprinters have more fast glycolytic fibers.

Muscle Hypertrophy and Atrophy

• Hypertrophy: Increase in muscle size due to exercise.

• Atrophy: Decrease in muscle size due to inactivity.

• Anabolic Steroids: Can increase muscle mass but have side effects.

Lecture 6: Motor Units and Muscle Contraction Types

Motor Units and Strength of Contraction

A motor unit consists of a motor neuron and all the muscle fibers it innervates. The number and size of motor units affect contraction strength.

• Small Motor Units: Fine control (e.g., eye muscles).

• Large Motor Units: Gross movements (e.g., thigh muscles).

Muscle Twitch, Summation, and Tetanus

• Muscle Twitch: Single contraction response to a stimulus.

• Summation: Increased contraction strength due to rapid stimuli.

• Tetanus: Sustained contraction due to high-frequency stimulation.

• Myogram: Graphical recording of muscle contraction.

Isotonic vs. Isometric Contraction

• Isotonic Contraction: Muscle changes length (concentric: shortens, eccentric: lengthens).

• Isometric Contraction: Muscle tension increases, but length does not change.

• Example: Lifting a weight (isotonic), holding a weight steady (isometric).

Summary Table: Types of Muscle Tissue

Key Equations

• ATP Hydrolysis:

• Force of Muscle Contraction:

Additional info: Academic context and examples have been added to clarify and expand upon the original brief points and questions.